Overload-indicating apparatus for transformers



Oct. 21,1924. I 1,512,817

D. BOYDEN OVERLOAD INDICATING APPARATUS FOR TRANSFORMERS Filed June 16.1921 Patented Get. 21, 192.4.

' unrraa sra'res DAVIS S. BOYDEN, OF ALLSTON, MASSACHUSETTS.

OVERLOAD-INDICATING APPARATUS F'Olit TRANSFORMERS.

Application filed June 16, 1921. Serial No. 473,205.

fl '0 all whom it may concern Be it known that I. DAVIS citizen of theUnited States, residing at .Allston, in the county of Suffolk and Stateof Massachusetts, have invented certain new and useful Improvements inOverload-Indicating Apparatus for Transformers; and I do hereby declarethe following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same.

The present invention relates to an improvement in overload indicatingapparatus for transformers. 7 3

The present invention constitutes an improvement upon the constructionillustrated and described in the application executed by me of even dateherewith for an improvement in transformers.

The object of the invention is to produce an overload indicatingapparatus having provision for indicating the attainment of differentdegrees of overload, and to this end the invention consists in theapparatus hereinafter described and particularly defined in the claims.

In the accompanying drawings illustrating the preferred form of theinvention, Fig. 1. is an elevation of a transformer showing the overloadindicating apparatus in posi= tion; Fig. 2 is a rear elevation of theapparatus with the box removed; Fig. 3 is a vertical section taken onthe line 3-3, Fig. 2, showing the box; Fig. {1 is a horizontal sectiontaken on the line 1- 1, Fig. 3; and Fig. 5 is' an enlarged detailhereinafter referred to. V

The overload indicating apparatus illus trated inthe drawings isdescribed as followsz This apparatus cons1sts of a heatsensitiveeleme'nt 10 supported on the lower end of a tube 11 from thebase 12, adapted to be inserted through the cover of the transformer 20,into the oil 21, and in close proximity to the coil 22. The instrumentis secured in 'place in the cover by means of a nipple 13 which isinserted in the hole in the cover of the transformer and secured inplace by a' nut mounted aplate 15 which carries standards 16 supportingtwo horizontalplates 17, 18. These standards and plates constitute theframe work of the indicating portion of the apparatus. The heatsensitive elementcom sists of a coil or spiral 30 of any usual or thetrip 7 lower end lof the spring detent 52, engages 14. Upon the base 12is preferred construction, to which is attached S. BoYonN, a

the vertical rod 31 adapted to be turned by the heat sensitive coil 30with variations in temperature of the oil in the transformer. The upperend of the rod 31 passes through a hole in the plate 17, which supportsand ,steadies the rod in position. Near the upper end ofthe rod 31 issecured a collar 32. Loosely mounted on theupper end of the rod andresting on the collar 32 is the trip disk 33, which is held from endwisemovement of the red by a collar 34. secured by a screw 35 to the rod 31.The trip disk 33 is provided with aipin 36, and the collar 3.4 isprovided with a pin 37. A hair spring 38 is bent upon itself andembraces the pin 36 at one end, and is secured to the pin 37 at theother end by means of a screw 39. The

disk33 is also provided with a second pin 10 against which thepin 37 isheld by the tendency ofthehair spring 38 to straighten out. Thisarrangement is such that the trip disk 33 is normally held in positionwith its pin 10 against the collar pin 37, so that as the temperaturerises, therod 31 turns counterclockwise, as viewed in Fig. 5,. and turnsthetrip disk by means of the engagement of the collar pin 37 with thedisk pin 40, The semaphoreoO is mounted to slide vertically on the rods51, which are sup'-. ported at the bottom in the plate 15 and at the topin 'the -plate 18. To the semaphore is attached a spring detent 52, thelower end of which normally. rests upon the upper surface of the tripdisk 33, as shown in Figs. 2,3 and 4 When the rod 31 is turned by a risein thetemperature, the trip disk moves counter-clockwise bringing thenotch in the disk'under the lower end of the spring ,detent; 52,cthereby permitting the semaphore 50 to fall. This spring detent,however, is provided'with'a shoulder 53,-which, when diskypasses outfrom under the the, trip disk inlthe descent of the, some phore. Thisarrests the descent of the semaphore before it has completed its fall.and holds the semaphore in what may be called its middle ortolerableoverload position.

until the f attainment of a second critical temperature, "when the tripdisk moves out fr-omunder the shoulder 53, thus permitting thesemaphoreto' complete its descent' Thusitwill belseen that in thisapparatus, upon the attainment of the firstcrit-ical temperature,thesemaphore drops to middle or tolerable overload position, andindicates the attainment of the first critical temperature. If thetemperature now turning of the rod 31 isnot prevented because the hairspring 38 permits the rod to turn, resisted only by the slightresistance oflfered by the hair spring to such return turning movement.If observed at this time, the observer will understand that thetemperature of the transformer rose to the first critical point,andgvhile it may have risen above that point, it did not attain thesecond critical point. He may then reset thesemaphoreby means of theresetting device, consisting of the lever 60, carrying the pin 61, whichis adapted to engage the under side of the semaphore 50, to lift it upwhen the push pin 62 is'pressed upward to actuate the resetting lever60, the latter being pivoted at 63 one. bracket in the upper end of astud 6 4, within whichthe push pin 62 is mounted. If the temperature ofthe transformer now rises to the firstcritical point, the semacured tothe phore will again drop to its middle position and rema n 111 thatposition unt l reset, or

until the second critical temperature is reached, when the semaphorewill be per? mitted to dro 3 to the limit of its descent.

' This semaphoreand the devices above'described are enclosed within abox 70, provided with a window 71, which box is seplate 15 by screwsentering through the screw-holes 72, and in the bottom of the plate 1 5.hen the first critical temperature is reached, the semaphore is halfexposed through the window 71. When the second critical temperatureisreached,

the semaphore is wholly exposed through the window 71. I

This overload indicating apparatus in use on transformers will,"therefore, indicate by the position of the semaphore whether or not thetransformer has been subjected to an overload, and whether or not suchoverload was the moderate overload corresponding to the middle positionof the semaphore, or the greater overload corresponding to theqbottomposition :of the semaphore. Thus the character of theoverload to whichtheindieating apparatus is subjected, is indicated. Thefmd'dle positionof the semaphore may con vei ently betaltenas nidicating a to ler,-

able overload, the bottom position of i V to indicate an intolerableoverload, so, that when a transformer is subjected to tolerable0verlo-ad,its identity may be noted and it may .be made the subject of aregular and frequent inspection, because it is a transformer which,while liable to intolerable overload, does not require immediatereplacement, whereas when a transformer shows intolerable overload, itshould be replaced at once.

- he em era e ts ir n hich any given transformer is located willdetermine falls, the

This fact renders any even when the transformer coils are hotter, withthe result that with the same overload indicating apparatus set forthesame critical temperatures, the liability of burning out willbegreater in winter than in summer,

as stated. The present overload indicating apparatus, since it has twoindications of overload, or two indications of arrival at highertemperatures, affords provision for indicating dangerous temperatureboth insummer and in winter. In sunnner upon the indication oftolerableoverload, or the attainment of av firstrcritical temperature, theobserver will reset or note the condition, and put the transformer underobservation. Then when in summer intolerable overload, or the secondcritical temperature point, is reached, the observer will 'know andunderstand that the transformer must be replaced by another of larger.capacity. In winter time, however, this semaphore, on the arrival ofwhat in summer would be a condition of tolerable overload, maybe takento indicate a condition of intolerable overload, and replacement of thetransformer should be made at once. So thea'pparatushas a doubletemperature indication in' summer,

anda single useful temperature or overload indicating provision inwinter.

Having thus described the invention, what is claimed is 5- 1. Overloadindicating apparatus for transformers having, in combination, a heatsensitive element, asem'aphore,a rod adapted to be rotated by the heatsensitive element provided with a trip disk connected tothe rod to yieldin one direction, and to be positively moved thereby in the otherdirection, said semaphore being provided with a part to engage the tripdisk.

2. Overload ind-i'cati g apparatus for transformers havingg incombination, a heatsensitiveelement, a semaphore, a trip memberconnected with the heat sensitive element, ,a detent connected'withthesema phore, the trip member and detent having provision, for pemitting movement of the semaphore from non-indicating position, first totolerable overload indicating position, and second to intolerableoverload" indicating position;

transformers having, in combination, a heat a semaphore,- a rotary tripsensitive element,

disk connected with and actuated by the heat sensitive element, a detentconnected with the semaphore having two portions adapted to engage thetrip disk at positions of the semaphore indicating normal load andtolerable overload.

4. Overload indicating apparatus for transformers having, incombination, a heat sensitive element, an indicator, and connectionsbetween the heat sensitive element and the indicator to normally retainthe indicator in inoperative position constructed and arranged to permittheindicator to move into position for indicating tolerable overload ata certain predetermined temperature and to a second position forindicating a greater overload at a higher predetermined temperature andfor preventing the indicator from moving to inoperative position.

5. Overload indicating apparatus for transformers having, incombination, a heat sensitive element, a semaphore, means for normallyretaining the semaphore in nonindicating position, and connectionsbetween the heat sensitive element and the retaining means for allowingthe semaphore to first move into and to be retained in tolerableoverload indicating position at a predetermined temperature and tothereafter move into and be retained in intolerable overload position ata higher predetermined temperature.

6. Overload indicating apparatus for transformers having, incombination, a heat sensitive element, a semaphore, and connectionsbetween the heat sensitive element and the semaphore to normally holdthe semaphore in non-indicating position con structed and arranged topermit the semaphore to move by a step-bystep movement for indicating aplurality of different overload conditions to which the transformer maybe subjected havingvprovision for retaining it in such position.

7. Overload indicating apparatus transformers having, in combination, aheat sensitive element, an indicator normally retained in a first fixednon-indicating position, and connections between the heat sensitiveelement and the indicator constructed and arranged to permit theindicator to first move to a second fixed position for indicatingtolerable overload, and then upon further increase in temperature to athird fixed position to indicate intole "able overload.

8. Overload indicating apparatus for transformers having, incombination, a casing, a heat-responsive element, a trip mechanismconnected with the heat-responsive element, a gravity actuatedsemaphore, and means cooperating with the trip mechanism for holding thesemaphore in non-warning position at normal temperature, means be ingprovided whereby a predetermined increase in temperature will permit thesemaphore to drop and stop at a predetermined point, indicatingtolerable overload, and to thereafter, upon increase in temperature,permit'the semaphore to drop another step to thereby indicateintolerable overload.

DAVIS S. BOYDEN.

for v

